Details
| Original language | English |
|---|---|
| Article number | 109118 |
| Journal | Materials and Design |
| Volume | 196 |
| Early online date | 3 Sept 2020 |
| Publication status | Published - Nov 2020 |
Abstract
Ferromagnetic shape-memory CoNiGa alloys have attracted much scientific interest due to their potential alternative use as high-temperature shape-memory alloys, bearing a high prospect for actuation and damping applications at elevated temperatures. Yet, polycrystalline CoNiGa, due to strong orientation dependence of transformation strains, suffers from intergranular fracture. Here, two multi-grain CoNiGa samples were prepared by a novel hot extrusion process that can promote favourable grain-boundary orientation distribution and improve the material's mechanical behaviour. The samples were investigated by multiple methods and their microstructural, magnetic, and mechanical properties are reported. It is found that a post-extrusion solutionising heat treatment leads to the formation of a two-phase oligocrystalline homogeneous microstructure consisting of an austenitic parent B2 phase and γ-CoNiGa precipitates. Reconstruction of the full 3D grain morphology revealed large, nearly spherical grains with no low-angle grain boundaries throughout the entire sample volume. The presence of γ precipitation affects the transformation behaviour of the samples, by lowering the martensitic transformation temperature, while, in conjunction with the oligocrystalline microstructure, it improves the ductility. Controlling the composition of the B2 matrix, as well as the phase fraction of the γ phase, is thus crucial for the optimal behaviour of the alloys.
Keywords
- Co-Ni-Ga, Ferromagnetic shape-memory alloy, Hot-extrusion, Laue three-dimensional neutron diffraction tomography, Martensitic transformation
ASJC Scopus subject areas
- Materials Science(all)
- General Materials Science
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
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In: Materials and Design, Vol. 196, 109118, 11.2020.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - A multiscale study of hot-extruded CoNiGa ferromagnetic shape-memory alloys
AU - Samothrakitis, Stavros
AU - Larsen, Camilla Buhl
AU - Woracek, Robin
AU - Heller, Luděk
AU - Kopeček, Jaromír
AU - Gerstein, Gregory
AU - Maier, Hans-Jürgen
AU - Rameš, Michal
AU - Tovar, Michael
AU - Šittner, Petr
AU - Schmidt, Søren
AU - Strobl, Markus
N1 - Funding Information: This study was supported by OP RDE , MEYS , under the project “European Spallation Source - participation of the Czech Republic - OP”, Reg. No. CZ.02.1.01/0.0/0.0/16_013/0001794; and the MEYS project Solid21 CZ.02.1.01/0.0/0.0/16_019/0000760. The magnetic measurements were carried out at MGML ( http://mgml.eu ), which is supported by MEYS within the program of Czech Research Infrastructures (project no. LM2018096). Michal Rameš would like to acknowledge support from CSF (grant No. 19-09882S ). Hans Jürgen Maier and Gregory Gerstein would like to acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within grant 388671975 . Funding Information: This study was supported by OP RDE, MEYS, under the project ?European Spallation Source - participation of the Czech Republic - OP?, Reg. No. CZ.02.1.01/0.0/0.0/16_013/0001794; and the MEYS project Solid21 CZ.02.1.01/0.0/0.0/16_019/0000760. The magnetic measurements were carried out at MGML (http://mgml.eu), which is supported by MEYS within the program of Czech Research Infrastructures (project no. LM2018096). Michal Rame? would like to acknowledge support from CSF (grant No. 19-09882S). Hans J?rgen Maier and Gregory Gerstein would like to acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within grant 388671975.
PY - 2020/11
Y1 - 2020/11
N2 - Ferromagnetic shape-memory CoNiGa alloys have attracted much scientific interest due to their potential alternative use as high-temperature shape-memory alloys, bearing a high prospect for actuation and damping applications at elevated temperatures. Yet, polycrystalline CoNiGa, due to strong orientation dependence of transformation strains, suffers from intergranular fracture. Here, two multi-grain CoNiGa samples were prepared by a novel hot extrusion process that can promote favourable grain-boundary orientation distribution and improve the material's mechanical behaviour. The samples were investigated by multiple methods and their microstructural, magnetic, and mechanical properties are reported. It is found that a post-extrusion solutionising heat treatment leads to the formation of a two-phase oligocrystalline homogeneous microstructure consisting of an austenitic parent B2 phase and γ-CoNiGa precipitates. Reconstruction of the full 3D grain morphology revealed large, nearly spherical grains with no low-angle grain boundaries throughout the entire sample volume. The presence of γ precipitation affects the transformation behaviour of the samples, by lowering the martensitic transformation temperature, while, in conjunction with the oligocrystalline microstructure, it improves the ductility. Controlling the composition of the B2 matrix, as well as the phase fraction of the γ phase, is thus crucial for the optimal behaviour of the alloys.
AB - Ferromagnetic shape-memory CoNiGa alloys have attracted much scientific interest due to their potential alternative use as high-temperature shape-memory alloys, bearing a high prospect for actuation and damping applications at elevated temperatures. Yet, polycrystalline CoNiGa, due to strong orientation dependence of transformation strains, suffers from intergranular fracture. Here, two multi-grain CoNiGa samples were prepared by a novel hot extrusion process that can promote favourable grain-boundary orientation distribution and improve the material's mechanical behaviour. The samples were investigated by multiple methods and their microstructural, magnetic, and mechanical properties are reported. It is found that a post-extrusion solutionising heat treatment leads to the formation of a two-phase oligocrystalline homogeneous microstructure consisting of an austenitic parent B2 phase and γ-CoNiGa precipitates. Reconstruction of the full 3D grain morphology revealed large, nearly spherical grains with no low-angle grain boundaries throughout the entire sample volume. The presence of γ precipitation affects the transformation behaviour of the samples, by lowering the martensitic transformation temperature, while, in conjunction with the oligocrystalline microstructure, it improves the ductility. Controlling the composition of the B2 matrix, as well as the phase fraction of the γ phase, is thus crucial for the optimal behaviour of the alloys.
KW - Co-Ni-Ga
KW - Ferromagnetic shape-memory alloy
KW - Hot-extrusion
KW - Laue three-dimensional neutron diffraction tomography
KW - Martensitic transformation
UR - http://www.scopus.com/inward/record.url?scp=85090743526&partnerID=8YFLogxK
U2 - 10.1016/j.matdes.2020.109118
DO - 10.1016/j.matdes.2020.109118
M3 - Article
AN - SCOPUS:85090743526
VL - 196
JO - Materials and Design
JF - Materials and Design
SN - 0264-1275
M1 - 109118
ER -